Currently, semiconductor memory, magnetic storage media, optical disks, and the like are presented as storage media. In particular, semiconductor memory, which is small and compact, has the characteristic that it can be electrically written or read at a high speed.
In a storage medium such as semiconductor memory, a single memory cell is required to be miniaturized to meet the demands for larger capacity or the like, but since a single memory cell requires a certain number of transistors and has a limitation in dimensions that can be processed due to a diffraction limit or the like in a fabrication process, there is a limitation in the miniaturization of a memory cell.
For this reason, in the related art, a phase change memory using a phase change material capable of further reducing the size of a single memory cell is disclosed. The phase change memory uses a phenomenon in which a phase change material has resistivity that greatly differs when the phase change material is in a crystalline state and an amorphous state.
However, in the related art, it is also disclosed that a phase change memory in which a phase change portion made of a phase change material is formed is to be perpendicular to a surface of a substrate for miniaturizing. However, in order to form such a phase change portion, it is required to form an opening portion to be perpendicular to the surface of the substrate and to bury the phase change material in the opening portion. For this reason, a film forming method such as sputtering cannot be used, and thus, a high-priced device is required due to limited types of film forming methods. In addition, when an organic metallic material is used as a raw material, carbon (C) or the like included in the organic metallic material is mixed as an impurity in the formed phase change portion, and thus reliability can be degraded.
Further, when the opening of the formed opening portion is narrow and deep, it is difficult to uniformly form a phase change material made of a ternary or quaternary compound without a defect or the like.